1. Field of the Invention
The present invention relates to an endoscope apparatus appropriate for an endoscope.
2. Description of the Related Art
Conventionally, endoscope apparatuses for performing observation of a site to be examined or various kinds of treatments by inserting an elongated endoscope into a body cavity or the like have been widely used. In such an endoscope apparatus, a light source apparatus is adopted to perform photographing inside the cavity. In recent years, there may be a case where a light source apparatus adopting a solid-state light-emitting element, such as an LED and a laser light source, as a light emitting portion is used. Such a light source apparatus can perform light adjustment control of the LED by PWM control for changing a duty ratio of a driving pulse or current control for changing an LED current.
By using solid-state light-emitting elements in a plurality of colors as solid-state light-emitting elements, such as LEDs and laser light sources, it is possible for the light source apparatus to emit illuminating light with arbitrary color balance. For example, Japanese Patent Application Laid-Open Publication No. 2011-36361 discloses an apparatus in which it is possible to change color balance of illuminating light with use of blue and violet laser light sources. In the case of a light source apparatus with LEDs also, it is similarly possible to radiate illuminating light having arbitrary color balance, for example, by adopting LEDs for respective colors of R, G and B.
Note that a light source apparatus for endoscope is required to emit a large amount of illuminating light. Therefore, an amount of light emission of each solid-state light-emitting element is large, and an amount of heat generation is also large. The solid-state light-emitting element, however, has a temperature characteristic that light emission efficiency decreases as temperature increases. Therefore, in the light source apparatus using solid-state light-emitting elements, it is necessary to adopt a cooling apparatus for cooling the solid-state light-emitting elements. For example, cooling members, such as a fan, a heat sink, a heat pipe and a Peltier element, are used in the cooling apparatus. As for the cooling members which require power, for example, by supplying sufficient power corresponding to a maximum amount of heat generation of the solid-state light-emitting elements to the cooling members, each of the solid-state light-emitting elements is sufficiently cooled to prevent the light emission efficiency from decreasing.
By the way, each image pickup device provided for an endoscope differs in a spectral sensitivity characteristic. Further, each light guiding optical system provided in an endoscope so as to guide illuminating light from a light source apparatus to an object differs in a spectral transmission characteristic. Therefore, in a case of using one light source apparatus for a plurality of kinds of endoscopes, it is necessary to adjust color balance of illuminating light according to the spectral sensitivity characteristic and spectral transmission characteristic of each endoscope. That is, it is necessary to cause an amount-of-light ratio, which is a ratio of amounts of light emission of light emitted from the solid-state light-emitting elements for the respective colors of the light source apparatus, to be changed according to the spectral sensitivity characteristic and spectral transmission characteristic of the endoscope. Further, color balance of required illuminating light differs in different observation modes, for example, a normal-light observation mode for performing observation using white color light, a special-light observation mode for obtaining particular information about an object by radiating light with a predetermined wavelength different from white color light to the object, and the like, and, therefore, it is necessary to cause the amount-of-light ratio of the solid-state light-emitting elements to change for the respective colors.